OTP Verification Logic & Countdown Timer Logic

A. OTP Verification Logic is the process of comparing the user-entered OTP with the originally generated OTP to confirm authenticity. It ensures that only correct input is accepted for successful verification.

Here, once the user enters all 4 digits, the system joins them into a single string and compares it with the generated OTP stored in the state.

The OTP is initially generated randomly and displayed in a browser alert when the user clicks Send OTP. If both values match, a success message is displayed; otherwise, an error message appears. This logic simulates real-world authentication behaviour.

B. Countdown Timer Logic is used to create a time-based restriction or delay, often for actions like resending OTP or retrying requests. It helps improve security and control user flow.

In this project, a 30-second timer starts after OTP is generated and displayed via alert. During this time, the resend button remains disabled.

The timer decreases by 1 second each second, and once it reaches 0, the resend OTP button becomes active again. This prevents repeated OTP generation and simulates real authentication systems where users must wait before requesting a new OTP.